Tissues

Tissues

collections of cells and cell products that perform specific, limited functions

Four types of tissue

epithelial, connective, muscle, neural

epithelial tissue

covers exposed surfaces, lines internal passageways, forms glands

connective tissue

fills internal spaces, provides structural support, stores energy

muscle tissue

Specialized for contraction. Skeletal muscle, heart muscle, and walls of hollow organs.

neural tissue

carries electrical signals from one part of the body to another

epithelia

layers of cells that cover internal or external surfaces

glands

structures that produce secretions

characteristics of epithelial tissue

cellularity, polarity, attachment, avascularity, regeneration

cellularity

cell junctions

Polarity

apical and basal surfaces

attachment

basement membrane or basal lamina

functions of epithelial tissue

physical protection, control permeability, provide sensation, produce specialized secretions

glandular epithelium

produces secretions

Maintaining the Integrity of Epithelia

Intercellular connections, attachment to basal lamina, epithelial maintenance and repair

Intercellular connections

Support and communication, cell adhesion molecules (CAMs), transmembrane proteins, proteoglycans act as intercellular cement, contain glycosaminoglycans such as hyaluronan (hyaluronic acid)

CAMs (cell adhesion molecules)

transmembrane proteins

intercellular cement

proteoglycans

Hyaluronan (hyaluronic acid)

glycosaminoglycans

Intercellular connections

Cell junctions. Form bonds with other cells or extracellular material; Tight junctions; Gap junctions; Desmosomes

tight junctions

Between two plasma membranes. Adhesion belt attaches to terminal web. Prevents passage of water and solutes. Isolates wastes in the lumen.

gap junctions

Allow rapid communication. Are held together by channel proteins (junctional proteins, connexons). Allow ions to pass. Coordinate contractions in heart muscle.

Demosomes

a structure by which two adjacent cells are attached, formed from protein plaques in the cell membranes linked by filaments.

spot demosomes

small discs connected to intermediate filaments; tie cells together, stabilizes cells but allows bending & twisting

Hemidesmosomes

attach cells to basement membrane

Epithelial Maintenance and Repair

Epithelia are replaced by division of germinative cells (stem cells). Near basement membrane.

Classes of Epithelia

squamous, cuboidal, columnar, simple, stratified

based on shape

squamous, cuboidal, columnar

squamous epithelium

thin and flat

cuboidal epithelium

square shaped

columnar epithelium

tall, slender rectangles

Based on layers

simple and stratified

simple epithelium

single layer of cells

stratified epithelium

several layers of cells

squamous epithelia

Simple squamous epithelium, Mesothelium, Endothelium

simple squamous epithelium

absorption and diffusion

Mesothelium

lines body cavities

endothelium

lines heart and blood vessels

locations of simple columnar epithelium

Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys

functions of simple columnar epithelium

protection, secretion, absorption

Locations of Pseudostratified Columnar Epithelium

lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of lungs

functions of pseudostratified columnar epithelium

Protection, secretion, move mucus with cilia

locations of stratified columnar epithelium

small areas of the pharynx, epiglottis, anus, mammary gland, salivary gland ducts, and urethra

functions of stratified columnar epithelium

protection

glandular epithelia

endocrine and exocrine glands

endocrine glands

release hormones into interstitial fluid; no ducts

exocrine glands

produce secretions onto epithelial surfaces through ducts

Modes of secretion of glandular epithelia

merocrine, apocrine, holocrine

merocrine secretion

Produced in Golgi apparatus, Released by vesicles (exocytosis), Ex. Sweat glands

apocrine secretion

Produced in Golgi apparatus. Released by shedding cytoplasm. Ex. Mammary glands

holocrine secretion

Released by cells bursting, killing gland cells. Gland cells replaced by stem cells. Ex: sebaceous glands

types of secretions

serous glands, mucous glands, mixed exocrine glands

serous glands

watery secretions

mucous glands

secrete mucins

mixed exocrine glands

both serous and mucous

unicellular glands

Mucous (goblet) cells are the only unicellular exocrine glands

mucous (goblet) cells

scattered among epithelia

multicellular glands

structure of duct, shape of secretory portion of gland, relationship between ducts and glandular areas

Structure of the Duct (Multicellular Glands)

simple (undivided), compound (divided)

Shape of secretory portion of the gland

tubular (tube shaped), alveolar or acinar (blind pockets)

relationship between ducts and glandular areas

branched (several secretory areas sharing one duct)

simple tubular gland

intestinal glands

simple coiled tubular

merocrine sweat glands

simple branched tubular

gastric glands, mucous glands of esophagus, tongue, duodenum

simple alveolar (acinar)

not found in adult; a stage in development of simple branched glands

simple branched alveolar

sebaceous (oil) glands

compound tubular

Mucous glands (in mouth), Bulbourethral glands (Male Reproductive System), Testes (seminiferous tubules)

compound alveolar (acinar)

mammary glands

compound tubuloalveolar

salivary glands, glands of respiratory passages, pancreas

characteristics of connective tissues

binds/supports/protects other tissues and organs, derived from mesenchyme (embryonic CT)

what makes up the matrix

ground substance and fibers

majority of tissue volume

matrix

functions of connective tissue

physical protection, support and structural framework, binding of structures, storage, transport, immune protection

classifying connective tissue

connective tissue proper, fluid connective tissue, supporting connective tissue

categories of connective tissue

loose and dense

loose connective tissue

more ground substance, fewer fibers ex: fat (adipose tissue)

dense connective tissue

more fibers, less ground substance (ex: tendons)

connective tissue proper cell populations

Fibroblasts, fibrocytes, adipocytes, mesenchymal, macrophages, mast cells, lymphocyte, microphages, melanocytes

Fibroblasts

most abundant, large, star-shaped, produce fibers

Fibrocytes

second most abundant cell type; found in all connective tissue proper; maintain the fibers of connective tissue proper

Adipocytes

fat cells that make up most of the subcutaneous layer

mesenchymal cells

stem cells that respond to injury or infection

Macrophages

eat pathogens and damaged cells

mast cells

stimulate inflammation after injury or infection

lymphocytes

specialized white blood cells that provide the body with immunity

lymphocytes develop into

T cells and B cells

What produces antibodies?

plasma cells

plasma cells are

B cells

Microphages

respond to signals from macrophages and mast cells

Melanocytes

Synthesize and store the brown pigment melanin

connective tissue fibers

collagen, elastic, reticular

collagen fibers

Most common protein in body; strong, flexible, inelastic

examples of collagen fibers

tendons and ligaments

reticular fibers

Network of thin, interwoven fibers, Extremely branched Stabilize functional cells and structures (soft skeleton). For example, supportive framework for spleen.

elastic fibers

contain elastin and recoil after stretching

example of elastic fibers

elastic ligaments of vertebrae

Example of reticular fibers

sheaths around organs

ground substance

unstructured material that fills the space between the cells and contains the fibers

Three types of loose connective tissue

areolar, adipose, reticular

areolar tissue

Elastic, supports organs, between muscles